. The Pharmaceutical era. equal arm balance is adapted to the widestrange of usefulness, and has been constructed of sucha degree of delicacy as to turn with one ten-millionthof the load in the pans. It is the type of constructionuniversally used in analytical balances and in all bal-ances of precision. UNEQUAL ARM BALANCE. In balances of unequal arms, as indicated by the name, the fulcrum is nearer to one end of the beam than to the other. This type of construction is based upon the principle that, when the arms of a lever are of unequallength, thepower andthe load areto eacho
. The Pharmaceutical era. equal arm balance is adapted to the widestrange of usefulness, and has been constructed of sucha degree of delicacy as to turn with one ten-millionthof the load in the pans. It is the type of constructionuniversally used in analytical balances and in all bal-ances of precision. UNEQUAL ARM BALANCE. In balances of unequal arms, as indicated by the name, the fulcrum is nearer to one end of the beam than to the other. This type of construction is based upon the principle that, when the arms of a lever are of unequallength, thepower andthe load areto eachother in-versely asthe lengthof the exam-ple, If thearm of the^^ lever whichsupports theweights isFig. 2.—Unequal Arm Balance. t w 1 c e the length of the arm which supports the substance to beweighed, then a given mass at the end of the longerarm wUl balance twice Its mass at the end of the shorterarm, and so on. The advantages of the unequal arm balance are thefacts that a small weight can be made to balance a. large mass, and that the same weight may be made tobalance different loads by varying its position on thelonger arm. The longer arm is commonly marked witha scale, and provided with a movable weight. Thefamiliar Grocers Scales are common examples. Theseare frequently constructed with two beams, so that thotare of a vessel in which a substance is to be weighedmay be taken with the movable weight on one beam,and the true or net weight of the substance with theother. These conveniences make them peculiarly well adaptedto commercial purposes, and they constitute perhapsthe greater number of weighing machines in use wheregreat accuracy is not required. NOTE.—By tare is meant the excess of the grossabove the net weight, as, for instance, the weight of avessel in which a substance is weighed. A tared vessel,then, is one whose weight or tare is known. By a combination of levers in such a way that theshort arm of one Is made to act upon the long arm ofanother, there
Size: 1826px × 1368px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, booksubjectdrugs, booksubjectpharmacy, bookyear1
